/*
* Copyright (c) 2013 Google, Inc.
*
* This software is provided 'as-is', without any express or implied
* warranty.  In no event will the authors be held liable for any damages
* arising from the use of this software.
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/
#ifndef B2_STACK_QUEUE
#define B2_STACK_QUEUE

#include "box2d/b2_stack_allocator.h"

template <typename T>
class b2StackQueue
{

public:

  b2StackQueue(b2StackAllocator *allocator, int32 capacity)
  { 
    capacity = b2Max(capacity, 32);
    m_allocator = allocator;
    m_buffer = (T*) m_allocator->Allocate(sizeof(T) * capacity);
    m_front = 0;
    m_back = 0;
    m_capacity = capacity;
  }

  ~b2StackQueue()
  {
    m_allocator->Free(m_buffer);
  }

  void Push(const T &item)
  {
    if (m_back >= m_capacity) {
      if (m_front > m_capacity / 4) {
        for (int32 i = m_front; i < m_back; i++) {
          m_buffer[i - m_front] = m_buffer[i];
        }

        m_back -= m_front;
        m_front = 0;
      } else {
        m_capacity *= 2;
        m_buffer = (T*) m_allocator->Reallocate(m_buffer, sizeof(T) * m_capacity);
      }
    }

    m_buffer[m_back] = item;
    m_back++;
  }

  void Pop()
  {
    b2Assert(m_front < m_back);
    m_front++;
  }

  bool Empty() const
  {
    b2Assert(m_front <= m_back);
    return m_front == m_back;
  }

  const T &Front() const
  {
    return m_buffer[m_front];
  }

private:

  b2StackAllocator *m_allocator;
  T* m_buffer;
  int32 m_front;
  int32 m_back;
  int32 m_capacity;

};

#endif
